The subject application relates to color scanning, and more particularly to highlight (HLC) color scanning to generate a ready-to-print dual-layer HLC image without having to process the image at a digital front end of a printing device.
A process referred to as “highlight color imaging” has been accomplished by employing basic xerographic techniques. The concept of tri-level, highlight color xerography is described in U.S. Pat. No. 4,078,929. That patent discloses the use of tri-level xerography as a means to achieve single-pass highlight color imaging. As disclosed therein, a charge pattern is developed with toner particles of first and second colors. The toner particles of one of the colors are positively charged and the toner particles of the other color are negatively charged. In one embodiment, the toner particles are supplied by a developer which comprises a mixture of triboelectrically relatively positive and relatively negative carrier beads. In another embodiment, the toner particles are presented to the charge pattern using a pair of magnetic brushes, each brush supplying a toner of one color and one charge. In yet another embodiment, the development systems are biased to approximately the background voltage. Such biasing results in a developed image of improved color sharpness.
By proper relation of operational control voltages and toner types, a highlight color printing machine can operate in one of three operational modes, namely “highlight color”, “monochrome-color” or “monochrome-black”. Additionally, the toner or marking material used to generate the highlight can assume one of a wide variety of colors. A print job is executed on the highlight color printing machine by providing a program indicating selections for color printing mode and marking material color. Moreover, many HLC commercial printing operations are characterized as “lights-out” facilities because many large print jobs are processed essentially continuously with little or no human intervention. Bulk printing machines are typically connected to a central job dispatcher through an electronic network. In those type applications, a fault condition causing a color printing delay which may arise due to failure of a xerographic sub-system, an inadequate supply of color toner, an improper color, or other reasons, can result in significant delays and potentially massive commercial losses.
With regard to scanners, if a customer desires a highlight color (HLC) print from a color scan, the color scan is delivered to the digital front end (DFE), which uses one of several algorithms to determine if the color scan pixels should be printed as a HLC or a black pixel. One problem is the regions that the customer believes should be rendered as pure black or pure HLC are instead “contaminated” with an undesirable color. The DFE color-to-HLC algorithms do not have the classification sophistication of the image processing available on modern production scanners to enable better HLC vs. black-and-white discrimination. Conventional processes for converting 24-bit color scans to two plane binary HLC print ready images on the DFE also limit productivity.
Many scan-to-HLC print applications are dependent on the color portion of the scanned page being rendered as pure HLC, and the black-and-white portion of the page being rendered as pure black-and-white. For example, black text being rendered with HLC mixed in is considered an image quality defect. Likewise, color markups rendered with black mixed in are also considered a defect. Color print jobs also are productivity limitation on DFEs of HLC print systems.
Accordingly, there is an unmet need for systems and/or methods that facilitate overcoming the aforementioned deficiencies.